Emulsions are widely used in numerous technical fields, given that they make possible the lasting combination of at least two immiscible liquid-liquid phases.
Emulsions can be classified into two main categories, oil-in-water emulsions and-water-in-oil emulsions. In oil-in-water emulsions, the continuous phase is water; oil droplets are dispersed in this phase. Conversely, in water-in-oil emulsions, the continuous phase is the oil, in which water droplets are dispersed.
In the present application, the term “stable emulsion ” is understood to mean an emulsion which does not exhibit phenomena of coalescence or phase separation after storage at ambient temperature for 6 months, preferably after storage at ambient temperature for 12 months and more preferably still at ambient temperature for 18 months.
The qualities required are different depending on the technical field in which the emulsions are employed. However, some qualities are desired for all emulsions, in particular stability over time and towards temperature variations, but also specific qualities in terms in particular of rheology, of stability with respect to pH variations or stability to electrolytes.
In the cosmetic, pharmaceutical or food fields, for example, emulsions have to exhibit numerous additional qualities, in particular in terms of appearance, of compatibility with active substances, of feeling to the touch, of feeling in the mouth, of fragrance, of acceptability with regard to dermatological or food use, and the like.
The emulsions obtained by conventional methods exhibit the disadvantage, however, of being highly sensitive, in particular to temperature and to dilution or to physicochemical parameters, such as the presence of electrolytes or variations in pH.
Any modification, however slight it may be, of the composition of an emulsion can have an influence on its stability and in a way which is difficult to predict. Thus, most of the time, a modification results in a modification in the qualities of the emulsion, indeed even a phase separation of the emulsion, and thus requires the development of a new appropriate formulation process.
Consequently, conventionally, when it is desired to introduce a new product into an emulsion in order to confer a given property or a given appearance thereon or else to increase or reduce the content of one of the constituents, it is necessary to define, by successive trial-and-error experiments, a new complete formulation protocol.
The present inventors have looked for a means for simplifying the work of formulators.